U.S. patent application number 11/082137 was filed with the patent office on 2006-04-13 for biometric information input device, biometric authentication device, biometric information processing method, and computer-readable recording medium recording biometric information processing program.
This patent application is currently assigned to Fujitsu Limited. Invention is credited to Yukihiro Abiko, Takashi Shinzaki.
Application Number | 20060078176 11/082137 |
Document ID | / |
Family ID | 35788234 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060078176 |
Kind Code |
A1 |
Abiko; Yukihiro ; et
al. |
April 13, 2006 |
Biometric information input device, biometric authentication
device, biometric information processing method, and
computer-readable recording medium recording biometric information
processing program
Abstract
The invention is a biometric information input device including
biometric information collection means for reading a
relatively-moving living body site and successively collecting a
plurality of partial images of the living body site as biometric
information, movement direction detection means for detecting a
movement direction of the living body site with respect to the
biometric information collection means based on the biometric
information collected by the biometric information collection
means, and coordinate conversion means for performing a coordinate
conversion on the biometric information collected by the biometric
information collection means using the movement direction detected
by the movement direction detection means, thereby allowing the
device to be used irrespective of a direction in which a living
body is swept when biometric information is entered.
Inventors: |
Abiko; Yukihiro; (Kawasaki,
JP) ; Shinzaki; Takashi; (Kawasaki, JP) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
Fujitsu Limited
Kawasaki
JP
|
Family ID: |
35788234 |
Appl. No.: |
11/082137 |
Filed: |
March 17, 2005 |
Current U.S.
Class: |
382/124 |
Current CPC
Class: |
G06K 9/00026 20130101;
G06F 2203/0338 20130101; G06F 3/03547 20130101 |
Class at
Publication: |
382/124 |
International
Class: |
G06K 9/00 20060101
G06K009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 2004 |
JP |
2004-296645 |
Claims
1. A biometric information input device comprising: biometric
information collection means reading a relatively-moving living
body site and successively collecting a plurality of partial images
of said living body site as biometric information; movement
direction detection means detecting a movement direction of said
living body site with respect to said biometric information
collection means based on said biometric information collected by
said biometric information collection means; and coordinate
conversion means performing a coordinate conversion on said
biometric information collected by said biometric information
collection means using said movement direction detected by said
movement direction detection means.
2. The biometric information input device according to claim 1,
further comprising movement direction search range reduction means,
when the same movement direction has been successively detected by
said movement direction detection means, reducing a movement
direction search range defined as a range over which said movement
direction detection means detects said movement direction to a
predetermined range including said detected movement direction.
3. The biometric information input device according to claim 1,
further comprising movement stop detection means detecting a stop
of movement of said living body site, wherein when the stop of
movement of said living body site has been detected by said
movement stop detection means, input of said biometric information
is stopped.
4. The biometric information input device according to claim 1,
further comprising biometric information display means displaying
biometric information coordinate-converted by said coordinate
conversion means.
5. A biometric authentication device comprising: biometric
information collection means reading a living body site to be
authenticated relatively moving and successively collecting a
plurality of partial images of said living body site as biometric
information; movement direction detection means detecting a
movement direction of said living body site with respect to said
biometric information collection means based on said biometric
information collected by said biometric information collection
means; coordinate conversion means performing a coordinate
conversion on said biometric information collected by said
biometric information collection means using said movement
direction detected by said movement direction detection means; and
authentication means performing authentication on said living body
site to be authenticated using results of said coordinate
conversion by said coordinate conversion means.
6. The biometric authentication device according to claim 5,
further comprising movement direction search range reduction means,
when the same movement direction has been successively detected by
said movement direction detection means, reducing a movement
direction search range defined as a range over which said movement
direction detection means detects said movement direction to a
predetermined range including said detected movement direction.
7. The biometric authentication device according to claim 5,
further comprising movement stop detection means detecting a stop
of movement of said living body site, wherein when the stop of
movement of said living body site has been detected by said
movement stop detection means, input of said biometric information
is stopped.
8. The biometric authentication device according to claim 5,
further comprising biometric information display means displaying
biometric information coordinate-converted by said coordinate
conversion means.
9. A biometric information processing method comprising the steps
of: a biometric information collection step of reading a
relatively-moving living body site, by means of biometric
information collection means, and successively collecting a
plurality of partial images of said living body site as biometric
information; a movement direction detection step of detecting a
movement direction of said living body site with respect to said
biometric information collection means based on said biometric
information collected in said biometric information collection
step; and a coordinate conversion step of performing a coordinate
conversion on said biometric information collected by said
biometric information collection means using said movement
direction detected in said movement direction detection step.
10. The biometric information processing method according to claim
9, further comprising a movement direction search range reduction
step of, when the same movement direction has been successively
detected in said movement direction detection step, reducing a
movement direction search range defined as a range over which said
movement direction is detected in said movement direction detection
step to a predetermined range including said detected movement
direction.
11. The biometric information processing method according to claim
9, further comprising a movement stop detection step of detecting a
stop of movement of said living body site and a stop step of, when
the stop of movement of said living body site has been detected in
said movement stop detection step, stopping input of said biometric
information.
12. The biometric information processing method according to claim
9, further comprising a biometric information display step of
displaying biometric information coordinate-converted by said
coordinate conversion means on display means.
13. A computer readable recording medium recording a biometric
information processing program for causing a computer to perform
the steps of: a biometric information collection step of reading a
relatively-moving living body site, by means of biometric
information collection means, and successively collecting a
plurality of partial images of said living body site as biometric
information; a movement direction detection step of detecting a
movement direction of said living body site with respect to said
biometric information collection means based on said biometric
information collected in said biometric information collection
step; and a coordinate conversion step of performing a coordinate
conversion on said biometric information collected by said
biometric information collection means using said movement
direction detected in said movement direction detection step.
14. The computer readable recording medium recording a biometric
information processing program according to claim 13, wherein said
computer is caused to perform a movement direction search range
reduction step of, when the same movement direction has been
successively detected in the case where said biometric information
processing program causes said computer to perform said movement
direction detection step, reducing a movement direction search
range defined as a range over which said movement direction is
detected in said movement direction detection step to a
predetermined range including said detected movement direction.
15. The computer readable recording medium recording a biometric
information processing program according to claim 13, wherein said
computer is caused to perform a movement stop detection step of
detecting a stop of movement of said living body site and a stop
step of, when the stop of movement of said living body site has
been detected in said movement stop detection step, stopping input
of said biometric information.
16. The computer readable recording medium recording a biometric
information processing program according to claim 13, wherein said
computer is caused to perform a biometric information display step
of displaying biometric information coordinate-converted by said
coordinate conversion means on display means.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a technology for processing
biometric information input for authentication, and particularly to
a method for partially and successively collecting biometric
information.
[0003] 2. Description of the Related Art
[0004] In a common biometric authentication device, biometric data
(enrollment data) is previously prepared (recorded) from biometric
information and further biometric data (matching data) is created
from biometric information to be authenticated, and then, the
matching data is compared to the enrollment data for
authentication.
[0005] For biometric authentication, biometric information that is
common to all persons and consistent throughout the lifetime of a
person (e.g., fingerprint, palm print, finger vein, palm vein,
etc.) is used, but there are problematic situations in which
authentication fails due to various factors.
[0006] Further, such authentication failures can be grouped into
two major factors. The first factor is that although both
enrollment data and matching data are related to the same person,
the person is falsely identified as a different person and such
case is called "false rejection". The second factor is that
although enrollment data and matching data are related to a
different person than a person himself/herself, the different
person is falsely identified as the person himself/herself and such
case is called "false acceptance".
[0007] Further, conventionally, a variety of methods for matching
biometric information have been put into practice, however, in some
of those methods, authentication sometimes fails due to rotational
displacement of biometric information. That is, when the degree of
freedom which is of the rotation of a living body relative to a
biometric information input device, or vice versa, is large,
rotational displacement exceeds an acceptable range for a matching
method and false rejection rate increases. Moreover, although a
method for repeating matching while rotating matching data or
enrollment data, in order to accommodate the degree of freedom in
the rotational direction, has been also known, rotating the
matching data or enrollment data sometimes causes matching data and
enrollment data corresponding to different persons to accidentally
match, leading to an increase in false acceptance rate.
[0008] A sweep fingerprint sensor has been known as a biometric
information input device. The sweep fingerprint sensor has a
rectangular collection surface (sensor surface/capturing surface)
of a small size and with a length substantially shorter than that
of a finger. Further, while a finger is moved relative to the
collection surface or the collection surface (fingerprint sensor)
is moved relative to the finger, a plurality of partial images of a
fingerprint of the finger are successively collected by a
fingerprint sensor and a total fingerprint image is reconstructed
by the collected partial images. Minutia information (ridge
bifurcation and ending) is extracted and created from the
reconstructed fingerprint image and the above personal
authentication is performed based on the information. Note that
relative movement of finger to the collection surface as described
above is called "sweeping" or "sliding".
[0009] A fingerprint reading device provided with such a sweep
fingerprint sensor is disclosed, for example, in the following
Patent Documents 1, 2. Further, a method for reconstructing a
fingerprint image using the amount of parallel movement and the
amount of rotational movement detected by the sweep fingerprint
sensor is disclosed in the following Patent Document 3.
[0010] As disclosed in the following Patent Documents 1 to 3, the
sweep fingerprint sensor operates so that relative position of a
sensor and a finger is changed and then the partial images of the
finger are input to the sensor in order. Note that hereinafter,
operation of changing the relative position of a sensor and a
finger is called "sliding" and a direction (movement direction of
finger) in which the relative position is changed is called "slide
direction". Typically, the sweep fingerprint sensor causes a finger
to slide relative to the sensor toward the front side (the side of
a subject to be authenticated), during which the sensor
successively acquires partial images of the finger.
[0011] For example, the above Patent Document 3 discloses a method
for detecting the slide direction and when the detected slide
direction is opposite to a previously expected direction,
interrupting input of fingerprint images. That is, a conventional
fingerprint image input device imposes a restriction on the slide
direction. [0012] [Patent Document 1] [0013] Japanese Patent
Laid-Open No. Hei 10-91769 [0014] [Patent Document 2] [0015]
Japanese Patent Laid-Open No. Hei 11-253428 [0016] [Patent Document
3] [0017] Japanese Patent Laid-Open No. 2004-110438
[0018] Recently, some of portable information processing devices
provided with a sweep fingerprint sensor and typified by laptop PC
(Personal Computer), PDAs (Personal Digital Assistants), portable
phone and the like are tailored to be used, oriented in the up/down
direction or left/right direction.
[0019] However, in such a conventional information processing
device, when a fingerprint image is input using a sweep fingerprint
sensor, the device has to cause a finger to slide in the previously
expected direction and therefore needs to rotate itself to read a
fingerprint, thereby disadvantageously increasing the degree of
complexity. Further, in a fingerprint image input device provided
with as a sweep fingerprint sensor that utilizes a change in
relative position of a sensor and a finger, it is desirable to
cause the sensor to be much more insensitive to the rotational
displacement of a fingerprint image due to the slide movement of
the finger.
[0020] Moreover, detection of the slide direction in the sweep
fingerprint sensor is achieved by comparing a plurality of
successive partial images acquired by the sensor and calculating a
relative position corresponding to the largest degree of overlap.
However, the sensor needs to acquire the partial images in a
shorter time interval so that the images are overlapped one another
even when a finger slides quickly, which imposes a heavy load on
the sensor to detect the slide direction. That is, a series of
processing steps requiring a large amount of calculations are
performed as follows. For example, the relative position of a
sensor and a finger is shifted little by little and the degree of
overlap in an overlap area of the images is determined, and then,
the slide direction is detected based on the relative position
corresponding to the largest degree of overlap. Therefore, there is
also a problematic situation in which the sensor needs to
efficiently detect the slide direction.
[0021] Additionally, an authentication technology using biometric
information utilizes, as biometric information, a site typified by
a body site such as a fingerprint having characteristics common to
all persons and consistent throughout the lifetime of a person.
However, even such biometric information could not cause a person
to be identified as the person himself/herself in the event where
different sites are input when enrolled and matched. This requires
the biometric information input device to increase reproducibility
of a position on which biometric information will be input.
[0022] In order to increase the reproducibility of a position on
which biometric information will be input, it is useful to allow a
user to view, for confirmation, the input biometric information
image. However, in a device tailored to be used, oriented in an
up/down or left/right direction, biometric information image to be
input is displaced in the rotational direction, potentially
preventing the user from viewing, for confirmation, the image
information. Accordingly, this also requires the device to display
biometric information image so that rotation of the device never
affects the display of the biometric information image.
[0023] Further, for example, if biometric information image is read
and a finger placed on the sensor is displaced significantly from
the center of the sensor, it is proposed that the device indicates
an instruction as a message, for example, "move your finger closer
to the right" to a user and instructs the user's finger to move to
an appropriate position on the sensor. However, for example, in a
device provided with a fingerprint sensor that can be used,
oriented in the up/down direction, a direction viewed from the
device and a direction viewed from the user are opposite in such an
upside down position of the sensor and therefore the device has to
take into account the status, etc., (orientation, pointing
direction) of the device in order to instruct the user to move
his/her finger in the proper direction, which imposes an additional
task on the device.
[0024] Further, it could also be proposed that a sweep fingerprint
sensor is used as a pointing device. However, in a device that can
be used, oriented in an up/down or left/right direction, when a
sweep fingerprint sensor is used as a pointing device, a direction
viewed from the device and a direction viewed from a user are
different and therefore direction information detected using a
pointing function is sometimes displaced from a direction the user
inputs.
SUMMARY OF THE INVENTION
[0025] The invention has been conceived in consideration of those
problems and is intended to allow a biometric information input
device to be used irrespective of a direction in which a living
body slides when biometric information is input.
[0026] Accordingly, a biometric information input device of the
invention is characterized in that the device includes biometric
information collection means for reading a relatively-moving living
body site and successively collecting a plurality of partial images
of the living body site as biometric information; movement
direction detection means for detecting a movement direction of the
living body site with respect to the biometric information
collection means based on the biometric information collected by
the biometric information collection means; and coordinate
conversion means for performing a coordinate conversion on the
biometric information collected by the biometric information
collection means using the movement direction detected by the
movement direction detection means.
[0027] Note that the device may include movement direction search
range reduction means for, when the same movement direction has
been successively detected by the movement direction detection
means, reducing a movement direction search range defined as a
range over which the movement direction detection means detects the
movement direction to a predetermined range including the detected
movement direction.
[0028] Further, the device may include movement stop detection
means for detecting a stop of movement of the living body site,
wherein when the stop of movement of the living body site has been
detected by the movement stop detection means, input of the
biometric information is stopped.
[0029] Still further, the device may include biometric information
display means for displaying biometric information
coordinate-converted by the coordinate conversion means.
[0030] Moreover, a biometric authentication device of the invention
is characterized in that the device includes biometric information
collection means for reading a relatively-moving living body site
to be authenticated and successively collecting a plurality of
partial images of the living body site as biometric information;
movement direction detection means for detecting a movement
direction of the living body site with respect to the biometric
information collection means based on the biometric information
collected by the biometric information collection means; coordinate
conversion means for performing a coordinate conversion on the
biometric information collected by the biometric information
collection means using the movement direction detected by the
movement direction detection means; and authentication means for
performing authentication on the living body site to be
authenticated using results of the coordinate conversion by the
coordinate conversion means.
[0031] Note that the device may include movement direction search
range reduction means for, when the same movement direction has
been successively detected by the movement direction detection
means, reducing a movement direction search range defined as a
range over which the movement direction detection means detects the
movement direction to a predetermined range including the detected
movement direction.
[0032] Further, the device may include movement stop detection
means for detecting a stop of movement of the living body site,
wherein when the stop of movement of the living body site has been
detected by the movement stop detection means, input of the
biometric information is stopped.
[0033] Still further, the device may display biometric information
coordinate-converted by the coordinate conversion means.
[0034] Moreover, a biometric information processing method of the
invention characterized in that the method includes the steps of: a
biometric information collection step of reading a
relatively-moving living body site by means of biometric
information collection means and successively collecting a
plurality of partial images of the living body site as biometric
information; a movement direction detection step of detecting a
movement direction of the living body site with respect to the
biometric information collection means based on the biometric
information collected in the biometric information collection step;
and a coordinate conversion step of performing a coordinate
conversion on the biometric information collected by the biometric
information collection means using the movement direction detected
in the movement direction detection step.
[0035] Note that the method may include a movement direction search
range reduction step of, when the same movement direction has been
successively detected in the movement direction detection step,
reducing a movement direction search range defined as a range over
which the movement direction is detected in the movement direction
detection step to a predetermined range including the detected
movement direction.
[0036] Further, the method may include a movement stop detection
step of detecting a stop of movement of the living body site and a
stop step of, when the stop of movement of the living body site has
been detected in the movement stop detection step, stopping input
of the biometric information.
[0037] Still further, the method may include a biometric
information display step of displaying biometric information
coordinate-converted by the coordinate conversion means on display
means.
[0038] Additionally, a biometric information processing program of
the invention is characterized in that the program causes a
computer to perform the steps of: a biometric information
collection step of reading a relatively-moving living body site by
means of biometric information collection means and successively
collecting a plurality of partial images of the living body site as
biometric information; a movement direction detection step of
detecting a movement direction of the living body site with respect
to the biometric information collection means based on the
biometric information collected in the biometric information
collection step; and a coordinate conversion step of performing a
coordinate conversion on the biometric information collected by the
biometric information collection means using the movement direction
detected in the movement direction detection step.
[0039] Note that the program may cause the computer to perform a
movement direction search range reduction step of, when the
computer is caused to perform the movement direction detection step
and the same movement direction has been successively detected,
reducing a movement direction search range defined as a range over
which the movement direction is detected in the movement direction
detection step to a predetermined range including the detected
movement direction.
[0040] Further, the program may cause the computer to perform a
movement stop detection step of detecting a stop of movement of the
living body site and a stop step of, when the stop of movement of
the living body site has been detected in the movement stop
detection step, stopping input of the biometric information.
[0041] Still further, the program may cause the computer to perform
a biometric information display step of displaying biometric
information coordinate-converted by the coordinate conversion means
on display means.
[0042] Additionally, a computer readable recording medium of the
invention is characterized in that the medium causes a computer to
perform the steps of: a biometric information collection step of
reading a relatively-moving living body site by means of biometric
information collection means and successively collecting a
plurality of partial images of the living body site as biometric
information; a movement direction detection step of detecting a
movement direction of the living body site with respect to the
biometric information collection means based on the biometric
information collected in the biometric information collection step;
and a coordinate conversion step of performing a coordinate
conversion on the biometric information collected by the biometric
information collection means using the movement direction detected
in the movement direction detection step.
[0043] Note that the biometric information processing program may
cause the computer to perform a movement direction search range
reduction step of, when the computer is caused to perform the
movement direction detection step and the same movement direction
has been successively detected, reducing a movement direction
search range defined as a range over which the movement direction
is detected in the movement direction detection step to a
predetermined range including the detected movement direction.
[0044] Further, the biometric information processing program may
cause the computer to perform a movement stop detection step of
detecting a stop of movement of the living body site and a stop
step of, when the stop of movement of the living body site has been
detected in the movement stop detection step, stopping input of the
biometric information.
[0045] Still further, the biometric information processing program
may cause the computer to perform a biometric information display
step of displaying biometric information coordinate-converted by
the coordinate conversion means on display means.
[0046] According to the invention, since the coordinate conversion
means performs a coordinate conversion on the collected biometric
information based on the movement direction detected by the
movement direction detection means from the biometric information,
even when an angular difference (rotational displacement) between
the biometric information collection means and the slide direction
of a living body occurs at the time of collection of biometric
information, the rotational direction can be corrected, allowing an
upright image to be reliably obtained. This allows an upright image
to be reliably obtained even when the slide direction changes each
time a living body slides and a rotational displacement from one
biometric information to another is observed.
[0047] Further, biometric information image can be obtained as an
upright image even if the biometric information is collected when
the orientation of the biometric information collection means is
changed, for example, the biometric authentication device is
rotated and used in an upside down position, and the biometric
information can be collected irrespective of the orientation of the
device, thereby allowing the device to be highly convenient.
[0048] Additionally, even when the display means is caused to
display the collected biometric information, the biometric
information can be acquired as an upright image irrespective of the
direction (orientation) of the device, display means, and biometric
information collection means, etc., and therefore there is no need
to detect and determine the direction (orientation) of the device,
display means, and biometric information collection means, etc.,
thereby eliminating the need for functions to perform such
detection and determination and reducing manufacturing cost.
[0049] Further, the degree of freedom of the mounting direction of
the biometric information collection means can be made high and
reduction in the mounting area of a wiring pattern leads to
reduction in the volume and price of the device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 is a block diagram illustrating a function
configuration (principal configuration) of a fingerprint
authentication device as one embodiment of the invention;
[0051] FIG. 2 is a block diagram illustrating a detailed
configuration of the fingerprint authentication device as one
embodiment of the invention;
[0052] FIG. 3 is a diagram illustrating an example of a movement
direction initial search range in the fingerprint authentication
device as one embodiment of the invention;
[0053] FIG. 4 is a diagram illustrating an example of the movement
direction initial search range in the fingerprint authentication
device as one embodiment of the invention;
[0054] FIG. 5 is a diagram illustrating another example of the
movement direction initial search range in the fingerprint
authentication device as one embodiment of the invention;
[0055] FIG. 6 is a diagram illustrating another example of the
movement direction initial search range in the fingerprint
authentication device as one embodiment of the invention;
[0056] FIG. 7 is a flow chart to explain how the movement direction
search range is set up in the fingerprint authentication device as
one embodiment of the invention;
[0057] FIG. 8 is a diagram illustrating a relationship between
biometric information images before and after coordinate conversion
in the authentication device as one embodiment of the
invention;
[0058] FIG. 9 is a diagram illustrating an example of how slide
speed of finger changes during collection of a fingerprint image in
a fingerprint sensor;
[0059] FIG. 10 is a diagram illustrating an example of a stop
monitoring range and movement direction initial search range in the
fingerprint authentication device as one embodiment of the
invention;
[0060] FIG. 11 is a flow chart to explain how a stop monitoring
range is set up in addition to the movement direction search range
in the fingerprint authentication device as one embodiment of the
invention;
[0061] FIGS. 12(a), 12(b) both are diagrams illustrating an example
of appearance of the authentication device as one embodiment of the
invention;
[0062] FIGS. 13(a), 13(b) are diagrams to explain an instruction
direction displayed on a display of the authentication device as
one embodiment of the invention;
[0063] FIG. 14 is a flow chart to explain how processing is
performed in the authentication device as one embodiment of the
invention;
[0064] FIG. 15 is a flow chart to explain how processing is
performed in the authentication device as one embodiment of the
invention;
[0065] FIG. 16 is a flow chart to explain how a biometric
information input step is performed in FIG. 14 and FIG. 15;
[0066] FIGS. 17(a), 17(b) are diagrams to explain a relationship
between a wiring pattern and mounting area in the fingerprint
sensor;
[0067] FIG. 18 is a block diagram illustrating a functional
configuration of a first modification of the fingerprint
authentication device as one embodiment of the invention;
[0068] FIG. 19 is a block diagram illustrating a functional
configuration of a second modification of the fingerprint
authentication device as one embodiment of the invention;
[0069] FIGS. 20(a), 20(b) both are diagrams illustrating an example
of appearance of the second modification of the fingerprint
authentication device as one embodiment of the invention;
[0070] FIG. 21 is a flow chart to explain how a movement direction
is corrected in the second modification of the fingerprint
authentication device as one embodiment of the invention;
[0071] FIG. 22 is a flow chart to explain how a movement direction
is corrected in the second modification of the fingerprint
authentication device as one embodiment of the invention;
[0072] FIGS. 23(a), 23(b), 23(c) are diagrams illustrating examples
in which the fingerprint authentication device of the invention is
applied to a mobile device (mobile phone) provided with a sweep
fingerprint sensor;
[0073] FIGS. 24(a), 24(b) are diagrams illustrating examples of
fingerprint images derived from images collected in the states of
FIGS. 23(b), 23(c);
[0074] FIGS. 25(a), 25(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (PDA: Personal Digital Assistants)
provided with a sweep fingerprint sensor;
[0075] FIGS. 26(a), 26(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (PDA) provided with the sweep
fingerprint sensor;
[0076] FIGS. 27(a), 27(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (PDA) provided with the sweep
fingerprint sensor;
[0077] FIGS. 28(a), 28(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (laptop PC (Personal Computer)) provided
with the sweep fingerprint sensor;
[0078] FIGS. 29(a), 29(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (tablet PC) provided with the sweep
fingerprint sensor; and
[0079] FIGS. 30(a), 30(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (tablet PC) provided with the sweep
fingerprint sensor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0080] Embodiments of the invention will be explained below with
reference to the accompanying drawings.
(A) Explanation of Embodiments
[0081] Both FIGS. 1 and 2 illustrate a fingerprint authentication
device (biometric information input device) as one embodiment of
the invention and FIG. 1 is a block diagram illustrating a function
configuration (principal configuration) of the device and FIG. 2 is
a block diagram illustrating a detailed configuration thereof,
where the same numerals are used to designate the same
elements.
[0082] Examples of biometric information primarily include a
fingerprint, palm print, finger vein, palm vein, etc., and in this
embodiment, a device using an image of fingerprint as biometric
information will be explained.
[0083] As shown in FIG. 1, a fingerprint authentication device 1
has functions as biometric information collection means 10 and
biometric information processing unit 110, and the biometric
information processing unit 110 has functions as movement direction
detection means 11, coordinate conversion means 14, position
detection means 16, instruction means 17, feature extraction means
32, matching degree calculation means 19, matching degree
determination means 20, biometric information central position
detection means 21, and storage means 22.
[0084] In practice, as shown in FIG. 2, the fingerprint
authentication device 1 of this embodiment is implemented by
providing a sweep fingerprint sensor 31 as biometric information
collection means 10 to a typical personal computer, etc., that
includes, for example, a real time clock 80, volatile memory unit
90, non-volatile memory unit 91 (storage means 22), display 81
(display means 15), and CPU (Central Processing Unit) 100.
[0085] In this case, later described functions as biometric
information processing unit 110 (movement direction detection means
11, coordinate conversion means 14, position detection means 16,
instruction means 17, feature extraction means 32, matching degree
calculation means 19, matching degree determination means 20),
feature extraction means 32, relative position detection means 33,
correction means 34, moving object detection means 35,
enrollment/matching data generating unit (generating means) 36, and
matching unit (matching degree calculation means 19, matching
degree determination means 20) 37 are implemented by running a
predetermined program (biometric information processing program) on
the CPU 100.
[0086] The sweep fingerprint sensor 31 (biometric information
collection means 10) is for visualizing biometric information of a
subject to be authenticated and successively collecting a plurality
of partial images (biometric information image) corresponding to
the biometric information (fingerprint). In more detail, the sensor
operates so that the sensor causes a finger (living body site) of
the subject to move relative to a collection surface (sensor
surface) while contacting the surface and successively collects
partial images of fingerprint of the finger, in order to read the
living body site during relative movement of the site and
successively collect a plurality of two-dimensionally arranged
partial images related to the living body site as biometric
information. Note that hereinafter, the sweep fingerprint sensor 31
is also referred to as a fingerprint sensor 31 for
simplification.
[0087] It should be appreciated that a method for collecting a
fingerprint image in the fingerprint sensor 31 may be implemented,
for example, by any one of an electrostatic capacitance method,
thermal sensing method, electric field method, and optical
method.
[0088] A fingerprint is being formed on outer skin (finger: living
body site) of a subject to be authenticated and the print pattern
of the fingerprint consists of a ridge (contact part) probably
brought into contact with the sensor surface and a valley
(non-contacting part/gap part) kept out of contact with the sensor
surface. The fingerprint sensor 31 utilizes a difference in its
sensitivity to a ridge part in contact with the sensor surface and
a valley part out of contact with the sensor surface and collects
partial fingerprint images as a multilevel image. The multilevel
image has different brightness varying depending on a distance from
the sensor, i.e., typically, the ridge part closer to the sensor is
displayed with a lower brightness and the valley part relatively
farther from the sensor is displayed with a higher brightness.
[0089] When requesting fingerprint authentication, the subject
moves his/her finger in an optional direction, for example, moves
the finger from bottom side to fingertip side or from finger's
right side to left side, while touching the sensor surface of the
fingerprint sensor 31 with his/her finger. Note that when the
device is provided with a mechanism for moving the fingerprint
sensor 31 relative to a finger, the subject needs not to move
his/her finger. Hereinafter, in this embodiment, the case where the
subject slides his/her finger from finger's bottom side to tip side
will be explained. Note that the configuration of the fingerprint
sensor 31 is well known in the art and therefore detailed
explanation thereof is omitted.
[0090] The real time clock 80 is used to add a time stamp to each
of the partial images successively collected by the fingerprint
sensor 31. Note that the real time clock 80 is not necessarily
provided when a certain time interval in which images are acquired
by the fingerprint sensor 31 is previously known and sufficiently
constant so as to allow ignorance of an error in the time
interval.
[0091] The volatile memory unit 90 is for storing information such
as partial images successively collected by the fingerprint sensor
31, characteristics, relative positions and post-correction results
obtained by the function of the CPU 100, and various types of
numerical values, needed to allow the CPU 100 to implement
functions as a fingerprint authentication device of this
embodiment.
[0092] The non-volatile memory unit 91 is for retaining previously
enrolled fingerprint data (enrollment data) related to the subject
and functioning as the storage means 22 in FIG. 1. The fingerprint
data retained in the non-volatile memory unit 91 could be the one
extracted from a fingerprint image collected by the typical
fingerprint sensor with a sensor surface larger than the size of a
finger, or enrollment data generated by the enrollment/matching
data generating unit 36 of this embodiment.
[0093] The display 81 (display means 15) is for displaying a
variety of images and information, functioning as biometric
information display means displaying biometric information
coordinate-converted by later-described coordinate conversion means
14, and further, displaying instruction given by the
later-described instruction means 17 to a user (subject).
[0094] The biometric information processing unit 110 is for
processing partial fingerprint images (biometric information)
collected by the fingerprint sensor 31 and has functions as
movement direction detection means 11, coordinate conversion means
14, position detection means 16, instruction means 17, feature
extraction means 32, matching degree calculation means 19, matching
degree determination means 20, and biometric information central
position detection means 21.
[0095] The movement direction detection means 11 is for detecting a
movement direction of a finger with respect to the fingerprint
sensor 31, based on partial fingerprint images collected by the
fingerprint sensor 31.
[0096] Further, the movement direction detection means 11 has
functions as movement direction search range reduction means 12 and
movement stop detection means 13. The movement direction search
range reduction means 12 is for reducing a movement direction
search range defined as a range over which a movement direction is
detected by the movement direction detection means 11, from a
previously set movement direction initial search range to a
predetermined range including the detected movement direction, when
the same movement direction has been successively detected by the
movement direction detection means 11.
[0097] FIGS. 3 and 4 are diagrams illustrating an example of a
movement direction initial search range in the fingerprint
authentication device 1 as one embodiment of the invention, wherein
a partial fingerprint image (denoted by a dashed line) detected at
time T-.DELTA.T by the fingerprint sensor 31 and the partial
fingerprint image (denoted by a solid line) detected after time
.DELTA.T has elapsed since then (at time T) are illustrated,
respectively, along with the movement direction initial search
range (denoted by a chain line) at time T.
[0098] That is, FIG. 3 and FIG. 4 are used to explain a range over
which one of the two fingerprint image is moved so that a position
with which the one fingerprint image is caused to overlap is moved
little by little in order to find a position in which two
fingerprint images corresponding to the same site just overlap with
each other, and in particular, to indicate the movement direction
initial search range. Note that an arrow drawn from the center of
the biometric information image collected at time T-.DELTA.T to the
center of the biometric information image collected at time T
represents a movement direction.
[0099] Note that FIG. 3 illustrates an example in which the
movement direction initial search range is in all directions (360
degrees) and centered on the fingerprint image (square in shape)
collected by the fingerprint sensor 31. In the example shown in
FIG. 3, the fingerprint sensor 31 is substantially square in shape
and the initial search range is set to 360 degrees when a movement
direction of a finger is not determined in an initial state. In the
example shown in FIG. 3, a maximum range for the movement direction
initial search range is Sx-Oxmin and Sy-Oymin in x-axis and y-axis
directions, respectively.
[0100] Note that Sy and Sx indicate sizes of the partial
fingerprint images in x-axis and y-axis directions, respectively,
when horizontal direction and vertical direction axes are defined
as x-axis and y-axis, respectively, for the partial fingerprint
image. Further, Oymin and Oxmin indicate sizes of a minimum
necessary area in y-axis and x-axis directions, respectively, which
area allows the sensor to determine that corresponding images
overlap with each other.
[0101] Further, FIG. 4 illustrates an example in which the movement
direction initial search range is in a minor axis direction
(up/down direction in FIG. 4) and centered on the fingerprint image
(rectangle in shape) collected by the fingerprint sensor 31. In the
example shown in FIG. 4, when the fingerprint sensor 31 is
rectangle in shape and the movement direction of a living body is
limited to the up/down direction in the initial state, the initial
search range is set to the up/down direction with respect to the
partial fingerprint image and cascade directions with respect to
the same.
[0102] A positional relationship between the respective images in
FIGS. 3 and 4 reflects a positional relationship between the finger
of a subject to be authenticated and the fingerprint sensor 31
during the elapsed time .DELTA.T between collection times
corresponding to the partial fingerprint images. For example, the
positional relationship represents a situation in which fingerprint
images are successively acquired when a finger is caused to slide
on the fingerprint sensor 31. That is, since a relative position of
the finger and the fingerprint sensor 31 is moving from time to
time, the fingerprint images collected at times T-.DELTA.T and T,
respectively, are the ones visualizing the sites that are slightly
displaced from one another.
[0103] Further, FIGS. 5 and 6 each are diagrams illustrating
another example of a movement direction initial search range in the
fingerprint authentication device 1 as one embodiment of the
invention and indicate situations in which the movement direction
initial search ranges shown in FIGS. 5 and 6, respectively, are
reduced (limited) to the downward direction. Note that in FIGS. 5
and 6, illustration of the biometric information image collected at
time T-.DELTA.T is omitted.
[0104] Then, how to set up the movement direction search range in
the fingerprint authentication device 1 as one embodiment of the
invention will be explained with reference to a flow chart (steps
A10 to A100) shown in FIG. 7.
[0105] First, a movement direction initial search range is set up
(step A10). The movement direction initial search range is
previously set up based on the slide direction in which the subject
potentially slides his/her finger with respect to the fingerprint
sensor 31 and determined depending on, for example, how this
fingerprint authentication device 1 is used and positions to which
the fingerprint sensor 31 is attached. Note that when the slide
direction on the fingerprint sensor 31 is not determined, it is
desirable to set up a wide movement direction initial search range,
as shown in FIGS. 3 and 4.
[0106] Next, partial fingerprint images are collected by the
fingerprint sensor 31 in order to update biometric information
image (step A20). Then, whether or not the movement direction
search range has been reduced is determined (step A30). In more
detail, whether or not a flag indicating that the movement
direction search range has been reduced is set to ON will be
determined in later described step A90. When the movement direction
search range has not been reduced (refer to NO route at step A30),
a movement direction is searched within the initial search range
(step A60).
[0107] That is, regarding a plurality of partial images
successively collected by the fingerprint sensor 31, whether or not
the movement directions are successively the same, i.e., whether or
not a finger moves in the same direction with respect to the
fingerprint sensor 31 is examined, and simultaneously, whether or
not the degree of overlap is above a predetermined threshold is
determined (step A70). Note that the degree of overlap implies the
degree of correlation or the degree of matching.
[0108] Now, the threshold used in step A70 will be explained. When
a subpixel error is present, images cannot be completely overlapped
with each other and therefore the degree of overlap is affected and
its value is reduced. In this case, since a fingerprint represents
projections and depressions, i.e., ridges and valleys on a finger
skin and the finger skin is soft, pressing a finger against the
sensor causes some distortion. Further, because the fingerprint
image is read during pressing of a finger against the sensor, the
distortion continuously changes. The degree of overlap is affected
also when the distortion occurs and its value is reduced. Various
other factors cause the degree of overlap to decrease and therefore
the extent to which the degree of overlap is reduced is
experimentally and analytically determined and then the threshold
is determined.
[0109] Additionally, the subpixel error is an error of less than
one pixel in a movement distance, caused by the quantization error
of an image. Although biometric information is digitized when the
information is converted to an image, the digitizing in practice
causes successive information to be decimated into discrete
information. In more detail, for example, when an image represented
by pixels spaced at a pitch of 50 micrometers and a movement
distance an object is less than 50 micrometers, the amount of
movement is in practice below one pixel.
[0110] However, when the sensor attempts to detect a movement
distance, one image that is caused to overlap the other is moved
only in units of pixels and therefore a movement distance less than
one pixel becomes equal to either one pixel or zero pixel. For
example, when an image comprised of pixels spaced at a pitch of 50
micrometers and the movement distance is 30 micrometers, the
distance is in practice determined to be one pixel rather than 0.6
pixels. In this case, an error of 0.4 pixel occurs and such an
error is referred to as a subpixel error.
[0111] Next, when the movement direction is kept unchanged and the
degree of overlap is not less than the threshold (refer to YES
route at step A70), whether or not a condition shown in step A70
has been satisfied consecutively N times or more is determined
(step A80). When the above condition has been satisfied
consecutively N times or more (refer to YES route at step A80), it
is determined that a finger is stably moving in the same direction
and the movement direction search range reduction means 12 reduces
(limits) the movement direction search range to a predetermined
range including its movement direction (step A90), and further sets
a flag indicating that the movement direction search range has been
reduced to ON.
[0112] Moreover, when a finger is not moving in the same direction
with respect to the fingerprint sensor 31 or the degree of overlap
is less than the predetermined threshold (refer to NO route at step
A70), or when the condition shown in step A70 has not been
satisfied consecutively N times or more (refer to NO route at step
A80), the process returns to step A20.
[0113] On the other hand, when the movement direction search range
has been reduced (refer to YES route at step A30), a movement
direction is searched within the reduced movement direction search
range (step A40) and further the movement direction search range is
updated so that the range becomes a predetermined range including
the movement direction searched in step A40 (step A50).
[0114] Subsequently, whether or not any more partial fingerprint
image collected by the fingerprint sensor 31 is present, or whether
or not finger movement is stopped is determined (step A100). When
the partial fingerprint image collected by the fingerprint sensor
31 is not present or the finger movement is stopped (refer to YES
route at step A100), the process is terminated. Further, when the
partial fingerprint image collected by the fingerprint sensor 31 is
present or the finger movement is not stopped (refer to NO route at
step A100), the process returns to step A20.
[0115] Next, slide speed detectable by this fingerprint
authentication device 1 is calculated using the following
mathematical relationship (1) in reference to coordinate system
used to express a fingerprint image. Vy<R(Sy-0ymin)/.DELTA.T,
Vx<R(Sx-0xmin)/.DELTA.T (1)
[0116] In this case, when a horizontal direction axis is defined to
be x-axis and a vertical direction axis is defined to be y-axis in
a partial fingerprint image, Vy and Vx are the y-axis direction
component and x-axis direction component of the slide speed,
respectively, and R is a pixel pitch. Note that although
expanding/contracting distortion and/or skew distortion appears on
the partial fingerprint image depending on the slide speed, the
above relationship is assumed to be valid in an ideal condition
free from such distortions.
[0117] Further, Vy and Vx vary depending on the features of a
living body to be input and .DELTA.T varies depending on the
performance of the fingerprint sensor 31 and significantly affects
determination of specification of the sensor. For example, when the
performance of the fingerprint sensor 31 is already fixed and
further when Sy and Sx are already determined, Oymin and Oxmin will
be experimentally determined.
[0118] Additionally, since .DELTA.T has a lower limit, the upper
limit of a detectable slide speed shown in the above relationship
(1) is represented by Vy and Vx. For example, when it is assumed
that a finger slides only in the y-axis direction, the performance
of the fingerprint sensor 31 is such that the lower limit of
.DELTA.T is 3 msec, Oymin is 4 pixels, Sy is 16 pixels, R is 0.05
mm/pixel, and the partial fingerprint image ideally contains no
distortion, the upper limit of the slide speed becomes 200
mm/sec.
[0119] However, as shown in the above example, the movement
direction detection means 11 has to operate following the slide
speed of a living body and detect movement directions from hundreds
of partial images per second, thereby putting a heavy load on the
means. In addition, when it is expected that the fingerprint
authentication device 1 is used, for example, in an upside down
state, the load is further increased. Therefore, the movement
direction detection means 11 utilizes inertia in order to
efficiently calculate the slide direction and then achieve
reduction in load imposed thereon.
[0120] That is, under the assumption that the slide direction does
not suddenly change in a short time interval, the detection means
determines that the slide direction corresponds to either one of a
positive direction or a negative direction along y-axis and since
then, limits a search area only within a range including the
determined direction in order to detect the slide direction. In the
above example, it is hardly expected that for example, a living
body or the fingerprint authentication device 1 moving at a speed
of 200 mm/sec as the upper limit speed in the slide direction
suddenly moves in the opposite direction after 0.003 msec has
elapsed.
[0121] Further, when reduction of the movement direction search
range is performed, it is important that the movement direction is
stable. A condition for determining stability of movement
direction, used as an example in the case shown in FIG. 7, is such
that the movement direction is kept unchanged and the degree of
overlap is above a predetermined threshold (see step A70).
[0122] Within the movement direction search range, it can be
assumed, based on the law of inertia after stabilization of the
slide direction, that a finger movement does not suddenly change
its direction. Accordingly, for example, the movement direction
search range is reduced to a range of the movement direction .+-.a.
Note that the search range may be generally either one of
upper/lower and left/right areas.
[0123] The movement stop detection means 13 is for detecting a stop
of movement of a finger (living body site) on the fingerprint
sensor 31. The fingerprint authentication device 1 operates so that
when the movement stop detection means 13 has detected the stop of
the finger movement of a subject to be authenticated, input of the
corresponding partial image is stopped.
[0124] As noted above, even if the movement direction search range
reduction means 12 reduces or decimates the search range in order
to reduce the amount of calculations required for detection of
movement direction, monitoring the stop of movement is
necessary.
[0125] For example, when the fingerprint sensor 31 is a sensor of
the type allowing reading of the image (partial image: biometric
information) of a fingerprint in the state of subject's finger
being in contact with a sensor unit (not shown) and further when
the skin of a living body is bent due to friction, etc., a site
contacting the sensor unit is, in some cases, hardly moved even if
the finger moves. As described above, even when pulling force
between the finger (living body) and the fingerprint sensor 31 is
created, monitoring the stop of the movement of living body is
needed to collect the partial fingerprint image in a condition free
from the influence of such pulling force.
[0126] FIG. 9 is a diagram illustrating an example of how the slide
speed of a finger changes during collection of the fingerprint
image in the fingerprint sensor 31, in which a solid line indicates
the case where a finger smoothly slides and a dashed line indicates
the case where pulling force between the finger and fingerprint
sensor 31 is created.
[0127] As shown in FIG. 9, there are the case where the slide speed
smoothly changes and the case where the slide speed largely changes
for the fingerprint sensor 31 to collect the fingerprint image. If
it can be assumed the slide speed changes smoothly, the movement
direction search range is limited to achieve reduction in
processing time and prevent erroneous detection. However, when the
bending of a skin due to friction between the living body and the
sensor occurs, the slide speed of a site contacting the sensor
temporarily and instantly becomes zero, as denoted by a dashed line
in FIG. 9, even if the living body itself is moving while
maintaining a constant speed.
[0128] The fingerprint authentication device 1 is configured so
that a movement speed estimate range is provided so as to set up a
stop monitoring range.
[0129] Here, how to set up the movement speed estimate range will
be explained. In step A90 (movement direction search range
reduction step) previously described with FIG. 7, under the
assumption of presence of inertia, speed is estimated using a
change in the amount of movement or a change in the slide speed
after stabilization of movement direction and the movement
direction search range is reduced. Note that similar discussion
with respect to x-axis direction and y-axis direction can be made
and therefore the slide speed is denoted by V, omitting attachment
of a subscript to V.
[0130] The slide speed V is apparently calculated using an imaging
time interval I(K) and a relative position Pr(K) for a partial
image, according to the following equation (2). V(K)=Pr(K)/I(K)
(2)
[0131] In this case, the imaging time interval I(K) means a period
of time from when imaging of a certain partial image is initiated
to imaging of a subsequent partial image is initiated.
[0132] Further, the relative position Pr'(K) assumed to
subsequently be detected is calculated according to the following
equation (3), using the above equation (2). Pr'(K)=V(K-1)*I(K), K:
integer (3)
[0133] When an image collecting time interval is sufficiently
short, the search range is considered less than one ridge width,
allowing further reduction in the number of computations and
reduction in the probability of danger of erroneous detection of
the relative position.
[0134] Note that when the imaging time interval I(K) can be
considered constant regardless of the time of imaging, utilizing
the latest relative position Pr(K-1) as it is as shown in the
following equation (4) brings about similar actions and effects to
those derived from the above equation (3). Pr'(K)=Pr(K-1) (4)
[0135] Such an estimate method becomes effective when it can be
assumed that a change in the slide speed is very slow and the speed
is constant.
[0136] When the imaging time interval I(K) can be considered
constant and a change in the slide speed is significant, the
relative position Pr'(K) may be estimated as in the following
equation (5). Pr'(K)=Pr(K-1)+[Pr(K-1)-Pr(K-2)] (5)
[0137] The above equation (5) is useful when a speed change
[Pr(K-1)-Pr(K-2)], i.e., acceleration can be assumed constant. For
example, application of the equation (5) to the case where the
slide speed changes so that the speed gradually increases during
slide initiation allows the search range to be appropriately set
up. Even when the imaging time interval I(K) cannot be considered
constant, adding a speed change based on a concept similar to the
above mentioned concept allows the search range to be appropriately
set up.
[0138] FIG. 10 is a diagram illustrating an example of a stop
monitoring range and movement direction initial search range in the
fingerprint authentication device 1 as one embodiment of the
invention, in which the partial image (denoted by a dashed line) of
a fingerprint detected at time T-.DELTA.T by the fingerprint sensor
31 and the partial image (denoted by a solid line) of a fingerprint
detected after time .DELTA.T has elapsed (at time T) are shown
along with the movement direction initial search range (denoted by
a chain line) and stop monitoring range at time T.
[0139] In FIG. 10, the stop monitoring range and movement direction
search range are drawn by superimposing the speed estimate range
and stop monitoring range related to the slide speed shown in FIG.
9 on the biometric information image collected at time
T-.DELTA.T.
[0140] Detection of the slide speed (movement direction and
movement distance) takes longer period of time as the search range
becomes wider. Accordingly, utilizing the fact that the slide speed
can be predicted to some extent based on its latest speed value
effectively limits the search range to a narrower range.
[0141] However, as shown in FIG. 9, in some cases, friction between
a finger and the fingerprint sensor 31 or existence of corners or
ledges in a housing around the perimeter of the sensor causes the
slide speed to suddenly become zero (pulling force occurs). When
such a temporal stop of the slide speed occurs, it is not
necessarily assured that the movement direction and movement
distance can be properly detected in a narrow search range.
[0142] Then, the fingerprint authentication device 1 is configured
so that in order to be able to properly detect the movement
direction and movement distance of a living body even when the
slide speed has suddenly changed to zero, the living body is
assumed to be only slightly displaced to a range from a reference
position (at the time point shown in the figure) referred to when
the movement distance is detected, and then, the range to which the
living body is slightly displaced is included in the search range.
The range slightly displaced from the reference position is
referred to as a stop monitoring range.
[0143] Next, how processing is performed when the stop monitoring
range is provided to the method, described according to the flow
chart shown in FIG. 7, for setting up a movement direction search
range in the previously described fingerprint authentication device
1 will be explained with reference to a flow chart (steps A10 to
A40, A51 to A57, A60 to A100) shown in FIG. 11.
[0144] Note that the same step number as the previously described
step number indicates the same or nearly the same processing and
therefore detailed explanation thereof is omitted.
[0145] In this method, when the movement direction initial search
range is set up, a stop monitoring count M is initialized to zero,
M=0 (step A10). Further, when the movement direction search range
is reduced (refer to YES route at step A30), the movement direction
is searched within the reduced movement direction search range
(reduced search range) (step A40) and a matching degree (maximum
matching degree) MAX_Cv representing the degree of overlap of
corresponding images within the movement speed estimate range is
calculated and stored in the non-volatile memory unit 90, etc.
(step A51).
[0146] Note that the matching degree means a matching degree to
which two successive partial images out of a plurality of partial
images collected by the fingerprint sensor 31 match each other. In
this embodiment, for two successive partial images, there are two
matching degrees, one calculated from the movement speed estimate
range and the other calculated from the stop monitoring range.
Comparison of the two matching degrees causes the movement distance
and movement direction to be obtained.
[0147] Further, when the subpixel error is present, one or more of
partial images are skipped until the movement distance reaches a
predetermined number of pixels or more. For example, when the
movement distance reaches in practice only 0.5 pixels, skipping one
partial image allows detection of one-pixel movement. Note that the
movement speed at this point is 0.5 pixels on average.
[0148] Subsequently, the movement speed estimate range is updated
(step A52) and the movement speed is searched within the stop
monitoring range (step A53). Further, the matching degree (maximum
matching degree) MAX_Cs representing the degree of overlap of
corresponding images in the stop monitoring range is calculated and
stored in the volatile memory unit 90, etc. (step A54).
[0149] Then, MAX_Cv and MAX_Cs are compared (step A55) and when
MAX_Cs is greater (refer to NO route at step A 55), a finger is
determined to be in a stop state and the stop monitoring count M is
incremented (step A 56). Further, when MAX_Cv is greater (refer to
YES route at step A55), a finger is determined to be in a movement
state and the stop monitoring count M is set to zero (step
A57).
[0150] Note that the stop monitoring count M is a counter used for
determination of continuation of a stop state and when the stop
state continues for a long period of time, i.e., the value of the
stop monitoring count M is beyond a threshold T, termination of
input of biometric information is determined, and when a finger is
temporarily in the stop state, detection of the movement direction
is continued.
[0151] That is, whether the stop monitoring count M is beyond the
threshold T or biometric information image is not present is
determined (step A100) and when the biometric information image is
not present or the stop monitoring count M is beyond the threshold
T (refer to YES route at step A100), termination of collection of
the partial image of a fingerprint is determined and the process is
terminated. Further, when the biometric information image is
present or the stop monitoring count M is below the threshold T
(refer to NO route at step A100), the process returns to step
A20.
[0152] Note that although in the example shown in FIG. 11, the
count M is used to determine the fact that the stop state has
continued for a long period of time and determination is performed
based on the count number in the count, the invention is not
limited to the above example, but for example, may be configured so
that the duration of continuation of a stop state is measured and
the duration is compared to a threshold. In this manner, various
modifications may be made without departing from the scope of the
invention.
[0153] A coordinate conversion means 14 is for using the movement
direction detected by a movement direction detection means 11 and
performing a coordinate conversion on biometric information
collected by the fingerprint sensor 31. Further, the coordinate
conversion means 14 is operable to use information indicative of a
difference between the movement direction detected by the movement
direction detection means 11 and a predetermined direction related
to the fingerprint sensor 31 for coordinate conversion.
[0154] Note that biometric information collected by the fingerprint
sensor 31 includes not only a fingerprint image (partial image)
collected by the fingerprint sensor 31 but also a variety of
information derived from the fingerprint image, for example,
minutiae information extracted from the fingerprint image.
Accordingly, the coordinate conversion means 14 may perform a
coordinate conversion on the minutiae information extracted from
the fingerprint image. Note that in this embodiment, an example in
which a partial fingerprint image is used as biometric information
and the coordinate conversion means 14 perform a coordinate
conversion on the partial image will be shown.
[0155] The coordinate conversion means 14 uses the movement
direction detected by the movement direction detection means 11 for
coordinate conversion of the partial fingerprint image collected by
the fingerprint sensor 31. In more detail, the coordinate
conversion is performed using then affine conversion as shown in
the following equation (6). ( x ' y ' ) = ( a b c d ) .times. ( x y
) + ( e f ) ( 6 ) ##EQU1##
[0156] For example, in the sweep fingerprint sensor, a site around
the first knuckle of a finger is placed on the sensor surface to
obtain the entire fingerprint image and the finger is caused to
slide until the finger tip is brought into contact with a biometric
information collection means 10. When a user operates the sensor,
he/she would be instructed to move his/her finger on the sensor as
if the finger is pulled back in front of him/her. Accordingly,
conversion is performed in such a way that the slide movement of
the finger always points in the vertical and downward direction
with respect to the biometric information image.
[0157] FIG. 8 is a diagram illustrating a relationship between
biometric information images before and after coordinate conversion
in the fingerprint authentication device 1 as one embodiment of the
invention.
[0158] When a coordinate system used to express the biometric
information image is the one shown in FIG. 8, a conversion equation
(7) is given as follows. ( x ' y ' ) = ( cos .times. .times.
.theta. - sin .times. .times. .theta. sin .times. .times. .theta.
cos .times. .times. .theta. ) .times. ( x - C x y - C y ) + ( C x C
y ) ( 7 ) ##EQU2##
[0159] In this case, .theta. is rotation angle, and Cx and Cy are
rotation centers in x-axis and y-axis directions. For example, the
rotation centers may be the image centers, Cx=Sx/2, Cy=Sy/2.
[0160] Further, when the amounts of movement of the biometric
information derived from the two successive biometric information
images are .DELTA.x and .DELTA.y in x-axis and y-axis directions,
respectively, the rotation angle .theta. is represented by the
following equations (8) to (11). i ) .times. .times. .DELTA.
.times. .times. x > 0 , .DELTA. .times. .times. y > 0 .times.
.times. ( first .times. .times. quadrant ) .times. .times. .theta.
= .pi. 4 - tan - 1 .function. ( .DELTA. y .DELTA. x ) ( 8 ) ii )
.times. .times. .DELTA. .times. .times. x < 0 , .DELTA. .times.
.times. y > 0 .times. .times. ( second .times. .times. quadrant
) .times. .times. .theta. = - .pi. 4 - tan - 1 .function. ( .DELTA.
y .DELTA. x ) ( 9 ) iii ) .times. .times. .DELTA. .times. .times. x
< 0 , .DELTA. .times. .times. y < 0 .times. .times. ( third
.times. .times. quadrant ) .times. .times. .theta. = - .pi. 4 - tan
- 1 .function. ( .DELTA. y .DELTA. x ) ( 10 ) iv ) .times. .times.
.DELTA. .times. .times. x > 0 , .DELTA. .times. .times. y < 0
.times. .times. ( fourth .times. .times. quadrant ) .times. .times.
.theta. = .pi. 4 - tan - 1 .function. ( .DELTA. y .DELTA. x ) ( 11
) ##EQU3##
[0161] The processing of coordinate conversion generally takes a
long period of time because conversion computation is made using a
rotating matrix containing trigonometric functions as described
above. Therefore, to avoid complexity, coordinate conversion taking
into account only the sign of Vy may be employed as simpler
coordinate conversion. That is, the conversion is performed in such
a way that a y-axis component of the slide direction points in a
vertical and downward direction with respect to the biometric
information image. In more detail, when the y-axis component of the
slide direction points in a vertical and upward direction with
respect to the biometric information image, the biometric
information image is rotated 180 degrees and then output. When the
image is simply rotated 180 degrees, conversion is completed only
by copying pixel values from one memory to another, allowing saving
of memory capacity and reduction in computation time.
[0162] If the duration required for processing is long, it is
proposed that angle information is not used in order to avoid
overhead, except that only rotation angle information is added to
the partial fingerprint image.
[0163] Both FIGS. 12(a), 12(b) are diagrams illustrating the
appearance of the fingerprint authentication device 1 as one
embodiment of the invention and FIG. 12(a) is a diagram
illustrating an example of the appearance of the fingerprint
authentication device 1, and FIG. 12(b) is a diagram illustrating
an example of the appearance of the fingerprint authentication
device 1 after modification.
[0164] The fingerprint authentication device 1 shown in FIGS.
12(a), 12(b) includes a main body 1a provided with a fingerprint
sensor 31 and a display unit 1b provided with a display 81, in
which the main body and the display unit are connected together so
that those two components are openablely by way of a two-axis hinge
(nail clipper designed hinge) 1c.
[0165] In more detail, as denoted by an arrow "a" in FIG. 12(a),
the display unit 1b can be rotated nearly 180 degrees about an axis
c1 of the two-axis hinge 1c relative to the main body 1a, thereby
allowing the main body 1a and display unit 1b to be folded in a
hinge-like manner. Further, as denoted by an arrow "b" in FIG.
12(a), the display unit 1b can be rotated about an axis c2 of the
two-axis hinge 1c, thereby allowing the display unit 1b to be
rotated 180 degrees.
[0166] Moreover, the display unit 1b in a state shown in FIG. 12(a)
is rotated respectively about the axes c1 and c2 of the two-axis
hinge 1c relative to the main body 1a, thereby allowing the main
body 1a and display unit 1b to be folded in such a manner that the
display 81 is exposed to a front of the device, as shown in FIG.
12(b).
[0167] Further, both the main body 1a and display unit 1b have a
rectangle shape and the main body 1a has a larger dimension than
the display unit 1b, along a direction orthogonal to the side
thereof used to provide connection with the display unit 1b via the
two-axis hinge 1c. Additionally, the fingerprint sensor 31 is
formed on an end portion of a surface of the main body 1a opposite
to the two-axis hinge 1c, which surface is to overlap the display
unit 1b.
[0168] This allows a subject to be authenticated to use the
fingerprint sensor 31 while viewing the display 81 in the unfolded
state of the main body 1a and display unit 1b, as shown in FIG.
12(a), and further to use the fingerprint sensor 31 while viewing
the display 81 even in the folded state of the main body 1a and
display unit 1b, as shown in FIG. 12(b).
[0169] That is, the fingerprint authentication device 1 is
configured as a laptop personal computer having the fingerprint
sensor 31 mounted on the main body la and tailored to rotate the
display unit 1b by 180 degrees and then fold the same. In this
case, it is assumed that the display 81 is mounted so that the
orientation of the display 81 is kept unchanged in both cases as
shown in FIG. 12(a) and in FIG. 12(b).
[0170] Then, as shown in FIG. 12(a), when the subject uses the
fingerprint sensor 31 in the unfolded state of the main body 1a and
display unit 1b (when using in an unfolded state), the subject
slides his/her finger in the direction from the two-axis hinge 1c
to the opposite end (front side) of the main body 1a, and as shown
in FIG. 12(b), when the subject uses the fingerprint sensor 31 in
the folded state of the main body 1a and display unit 1b (when
using in a folded state), the subject slides his/her finger in a
direction from the opposite end of the main body 1a to the two-axis
hinge 1c.
[0171] Note that when the display unit 1b in a state shown in FIG.
12(a) is rotated to a state shown in FIG. 12(b), the fingerprint
sensor 31 is brought into a state in which the sensor is rotated
180 degrees when viewed from the subject.
[0172] As described above, although in the fingerprint
authentication device 1, the slide directions of a finger on the
fingerprint sensor 31 in the unfolded state as shown in FIG. 12(a)
and in the folded state as shown in FIG. 12(b) are opposite, the
coordinate conversion means 14 in the fingerprint authentication
device 1 performs a coordinate conversion on the partial
fingerprint image depending on the slide direction.
[0173] In more detail, based on the fact that the slide direction
on the fingerprint sensor 31 is being rotated 180 degrees relative
to the slide direction on the fingerprint sensor 31 in the unfolded
state, the coordinate conversion means 14 performs a coordinate
conversion as described above so that the partial fingerprint image
collected by the fingerprint sensor 31 is rotated 180 degrees.
[0174] Accordingly, as shown in FIG. 12(b), an upright fingerprint
image (partial image) is displayed on the display 81 even in the
folded state, preventing the biometric information image from being
reversed in the up/down or left/right direction and the subject
from feeling odd.
[0175] That is, when the fingerprint image is input, a user will
simply slide his/her finger on the fingerprint sensor 31 so that
the finger is always pulled towards a front of him/her.
[0176] FIGS. 13(a), 13(b) are diagrams to explain instruction
directions displayed on the display 81 of the fingerprint
authentication device 1 as one embodiment of the invention.
[0177] A position detection means 16 is for detecting a position of
the finger of the subject relative to the fingerprint sensor 31 and
an instruction means 17 is for instructing and prompting the
subject to move his/her finger, based on the subject's finger
position detected by the fingerprint sensor 31, so that the
subject's finger is disposed in a position in which the finger is
to be placed on the fingerprint sensor 31. For example, an
instruction for the subject to promptly move his/her finger is
displayed on the display 81, along with a direction in which the
finger is to be moved.
[0178] For example, as shown in FIGS. 13(a), 13(b), in the
fingerprint authentication device 1 having the fingerprint sensor
31 mounted on the main body 1a and being capable of folding the
display unit 1b in a state in which the unit is being reversed by
the two-axis hinge 1c, it is assumed that the display 81 is mounted
so that the orientation of the display 81 is kept unchanged when
viewed from the subject, regardless of whether the device is used
in the unfolded state of the main body 1a and display unit 1b as
shown in FIG. 13(a) or in the folded state of the main body 1a and
display unit 1b as shown in FIG. 13(b).
[0179] As described above, although when the fingerprint
authentication device 1 reads a fingerprint, the slide directions
of a finger on the fingerprint sensor 31 in the unfolded state
(shown in FIG. 13(a)) and in the folded state (shown in FIG. 13(b))
are opposite, the subject may simply slide his/her finger on the
fingerprint sensor 31 so that the finger is always pulled toward a
front of him/her when inputting the fingerprint image. In this
case, when the slide direction and the vertical/downward direction
on the display 81 match, the subject may be properly
instructed.
[0180] That is, based on the slide direction detected by the
movement direction detection means 11, the coordinate conversion
means 14 performs a coordinate conversion so that the partial
fingerprint image collected by the fingerprint sensor 31 is
reversed in the up/down or left/right direction. Or, the
instruction means 17 instructs the subject to slide his/her finger
in the reversed up/down or left/right direction, based on the
detected slide direction. Note that in the example shown in FIGS.
13(a), 13(b), a direction in which the subject should slide his/her
finger is displayed as an arrow on the display 81 for the purpose
of warning to the subject.
[0181] Next, the position detection means 16 will be explained in
detail. The position detection means 16 is operable to detect an
area containing biometric information from the image acquired by
the fingerprint sensor 31. For example, when a living body to be
subjected to this treatment is a fingerprint, the biometric
information image expressed by a ridge having a larger pixel value
than a valley is assumed. Further, when the living body is hand
vascular, palm vein or finger vein, the biometric information image
expressed by a vein having a larger pixel value than a blood vessel
other than a vein is assumed. Further, when the above relationship
is opposite, brightness inversion techniques are applied to the
image and then the same discussion holds true for the image.
[0182] In order to determine the position of a living body directly
from the biometric information image, it is useful to determine a
gravity center from pixel values of the biometric information
image. Further, in order to determine the position more accurately,
it is conceived that an area containing the biometric information
image is extracted and then the gravity center is determined.
[0183] Note that hereinafter, the area containing the biometric
information is referred to as a biometric information area. To
extraction of the biometric information area, a general binary
method or clustering method can be applied. There is a simplest
method in which a predetermined threshold is defined as a certain
pixel value and pixels having a value greater than the threshold
are extracted as biometric information. Use of the gravity center
and variance of the extracted pixels allows detection of the
position of the biometric information area.
[0184] Next, the instruction means 17 will be explained. The
instruction means 17 performs instructions using difference
information Dx, Dy indicative of differences between positions Bx,
By detected by the position detection means 16 and the
corresponding central positions Cx, Cy of the fingerprint sensor
31. In more detail, if Dx=Bx-Cx, Dy=By-Cy and instruction
directions are Ix, Iy, the resulting instruction directions are
determined as Ix=-Dx, Iy=-Dy, as inversions of the difference
information Dx, Dy.
[0185] For example, when the finger of the subject is positioned to
the right relative to the fingerprint sensor 31, the instruction
means 17 instructs the subject to move the living body (finger) to
the left. In this case, the instruction is done, for example, by
displaying a mark indicating a direction as a left-pointing arrow,
etc., on the display 81. Further, in this case, directional
instruction may be not displayed in a detailed fashion, but only
one chosen out of constituent instruction directions and having a
greater magnitude than the others is displayed, for example, using
a step size of 90 degrees.
[0186] In this case, when a rotational displacement is present
between the fingerprint sensor 31 and display 81, instruction on
the display 81 (instruction means 17) becomes meaningless and
therefore the displacement is corrected using difference
information .theta. indicative of a difference between the movement
direction detected by the fingerprint sensor 31 from the biometric
information and a predetermined direction. If corrected directions
are Ix', Iy', Ix', Iy' are represented by the following equation
(12). ( I x ' I y ' ) = ( cos .times. .times. .theta. - sin .times.
.times. .theta. sin .times. .times. .theta. cos .times. .times.
.theta. ) .times. ( I x I y ) ( 12 ) ##EQU4##
[0187] A feature extraction means 32 is for extracting the features
of each partial image and the positions of the features from each
of a plurality of partial images collected by the fingerprint
sensor 31. In this case, as the features, both the foreground of
each partial image (value of brightness of a ridge image in the
embodiment) and the edges of the foreground (value of brightness
gradient in the embodiment) may be extracted or ridge end and
bifurcation may be extracted from a pattern created by changing the
foreground (e.g., ridge image) of each partial image to thin
lines.
[0188] A relative position detection means 33 is for detecting a
relative position of two partial images based on the features
(extracted by the feature extraction means 32) present in the area
where two successive partial images out of a plurality of partial
images collected by the fingerprint sensor 31 overlap with each
other. In this case, the relative position detection means 33 may
detect the above relative position with reference to one or more
relative positions detected until the current detection is
initiated, or may detect the above relative position with reference
to a relative position that has been estimated based on one or more
relative positions detected until the current detection is
initiated and is to be subsequently detected.
[0189] Further, the relative position detection means 33 may be
configured to group individual partial images successively
collected by the fingerprint sensor 31 into two or more partial
areas sharing a common area where these partial areas overlap with
one another and then process these partial areas, and detect the
above relative position for each of the two or more partial
areas.
[0190] A correction means 34 is for correcting image distortion due
to detection delay in the fingerprint sensor 31 or distortion due
to deformation of finger. The correction means 34 has the following
two types of correction functions. According to the first
correction function, the amount of feature distortion (amount of
distortion due to finger deformation) is calculated based on the
relative position detected by the relative position detection means
33 and the position of features of each partial image, and the
position of features of each partial image is corrected based on
the calculated amount of distortion. Moreover, according to the
second correction function, the position of features of each
partial image is corrected so as to eliminate the distortion
(expanding/contracting distortion and/or skew distortion) of each
partial image due to delay in collection by the fingerprint sensor
31 based on a time interval for collection of each partial image by
the fingerprint sensor 31, delay caused when the fingerprint sensor
31 collects each partial image, and the relative position detected
by the relative position detection means 33, in order to acquire
the relative position of features.
[0191] Note that when the relative position detection means 33 is
configured to group individual partial images successively
collected by the fingerprint sensor 31 into two or more partial
areas sharing a common area where these partial areas overlap with
one another and then process these partial areas, and detect the
above relative position for each of the two or more partial areas,
the correction means 34 corrects the position of features so that
the distortion of each partial image due to delay in collection by
the fingerprint sensor 31 is eliminated.
[0192] Further, the correction means 34 needs to be provided when
distortion occurs in an image collected by the fingerprint sensor
31 and the correction means 34 is not necessarily provided when the
fingerprint sensor 31 is able to ignore the distortion of the
image.
[0193] A moving object detection means 35 is for detecting
presence/absence of a movement object (in this case, subject's
finger) moving relative to the fingerprint sensor 31 based on a
plurality of partial images collected by the fingerprint sensor 31
and for example, is operable to calculate the weighted mean image
of partial images that have been collected by the fingerprint
sensor 31 until the current collection is initiated and detect
presence/absence of the movement object based on the calculated
weighted mean image. In more detail, the moving object detection
means 35 is operable to detect the existence of the movement object
when the value of a difference between latest partial image
collected by the fingerprint sensor 31 and the calculated weighted
mean image exceeds a predetermined threshold, and the predetermined
threshold is set to a value greater than the value of variation due
to noise.
[0194] An enrollment/matching data generating unit (generating
means) 36 is for using the features extracted by the feature
extraction means 32 and the relative position of features acquired
by the correction means 34 and then generating fingerprint data
(enrollment data and matching data) used to identify, for
authentication, a subject as the person himself/herself. When
enrollment of fingerprint data is performed, the fingerprint data
(known information such as positions and pattern of ridge
bifurcation and end) generated by the enrollment/matching data
generating unit 36 is enrolled and then stored as enrollment data
in a non-volatile memory unit 91. When a subject is going to be
identified as the person himself/herself, the fingerprint data
(information about ridge bifurcation and end) generated by the
enrollment/matching data generating unit 36 is sent as matching
data to a matching unit 37.
[0195] The matching unit (matching means) 37 is for comparing the
matching data generated by the enrollment/matching data generating
unit 36 and the subject's enrollment data stored in the
non-volatile memory unit 91 in order to perform matching and then
identify, for authentication, a subject as the person
himself/herself. The matching unit 37 is configured so that the
features and relative position obtained from partial images
visualized at earlier time points (time points recorded as a time
stamp value by a real time clock 80) by the fingerprint sensor 31
are preferentially used to perform the above matching which is
completed upon confirmation of matching results for the
subject.
[0196] The matching unit 35 comprises a matching degree calculation
means 19 and matching degree determination means 20. The matching
degree calculation means 19 is for calculating the degree of
matching between the matching data generated by the
enrollment/matching data generating unit 36 and the subject's
enrollment data stored in the non-volatile memory unit 91. Note
that for example, a correlation coefficient in a cross-correlation
method is used as the degree of matching.
[0197] Further, the matching degree determination means 20 is
operable to determine, based on the degree of matching calculated
by the matching degree calculation means 19, that the matching data
generated by the enrollment/matching data generating unit 36 and
the subject's enrollment data stored in the non-volatile memory
unit 91 match, for example, when the degree of matching is greater
than a previously defined threshold, in order to identify, for
authentication, the subject as an enrollment himself/herself who
enrolled the corresponding enrollment data.
[0198] How processing is performed in the fingerprint
authentication device 1 configured as above and as one embodiment
of the invention will be explained with reference to flow charts
shown in FIGS. 14 to 16. FIG. 14 is a flow chart (steps C10 to C40)
for explanation of how the enrollment data is enrolled in the
fingerprint authentication device 1 as one embodiment of the
invention, FIG. 15 is a flow chart (steps D10 to D60) for
explanation of how the matching is performed, and FIG. 16 is a flow
chart (steps E10-E30) for explanation of how steps of inputting
biometric information are performed in FIGS. 14 and 15.
[0199] When enrollment processing is performed, a subject uses the
biometric information collection means 10 (fingerprint sensor 31)
to perform input of biometric information (fingerprint) (step C10).
A feature extraction unit 32 performs extraction of characteristics
based on biometric information input through the fingerprint sensor
31 (step C20) and the enrollment/matching data generating unit 36
generates biometric data (step C30), and the generated biometric
data is recorded in the non-volatile memory 91 (storage means 22)
(step C40).
[0200] Further, when the matching is performed, input of biometric
information (fingerprint) is done using the biometric information
collection means 10 (fingerprint sensor 31) (step D10). The feature
extraction unit 32 performs extraction of features based on the
biometric information input through the fingerprint sensor 31 (step
D20) in order to generate biometric data (step D30). Then, the
matching degree calculation means 19 retrieves the biometric data
stored in the non-volatile memory 91 (storage means 22) (step D40)
in order to perform calculation of the degree of matching (step
D50) and the matching degree determination means 20 performs
determination based on the calculated degree of matching (step
D60).
[0201] Additionally, the above-described input of biometric
information in step C10 of FIG. 14 and step D10 of FIG. 15 is done
in accordance with the flow chart shown in FIG. 16. That is, after
the partial image of a living body site has been read by the
biometric information collection means 10 (step E10) detection of
movement distance is performed based on the collected biometric
information (step E20), after which partial images are combined
(step E30).
[0202] Note that in the flow chart shown in FIG. 16, illustration
of loop concept is omitted. For example, a movement distance
detection step denoted as step E20 may be initiated after a
biometric information reading step, denoted as step E10, has been
repeatedly performed on a plurality of partial images, or an image
combining step denoted as step E30 may be initiated after the
biometric information reading step denoted as step E10 and movement
distance detection step denoted as step E20 have been repeatedly
performed, or alternatively, the biometric information reading step
denoted as step E10, movement distance detection step denoted as
step E20 and image combining step denoted as step E30 may be
repeatedly performed, meaning that various modifications may be
made without departing the scope of the invention.
[0203] Further, determination of such loop termination can be
performed using combination of optional elements such as elapsed
time, the number of readings, movement distance, movement stop,
available buffer capacity, and the fact that an image has no
contents. Note that the determination of loop termination using the
movement distance out of these elements can be performed after
detection of movement distance.
[0204] Moreover, the processing previously described with reference
to the flow charts shown in FIGS. 7, 11 corresponds to the
biometric information input steps denoted as step C10 of FIG. 14
and step D10 of FIG. 15, and further to the biometric information
reading step denoted as step E10 and movement distance detection
step denoted as step E20 of FIG. 16.
[0205] As described above, according to the fingerprint
authentication device 1 as one embodiment of the invention, since
the coordinate conversion means 14 performs a coordinate conversion
on the collected biometric information based on the movement
direction from the biometric information detected by the movement
direction detection means 11, even when an angular difference
(rotational displacement) between the most preferable slide
direction on the fingerprint sensor 31 (e.g., normal line direction
passing through the center of the fingerprint sensor 31) and the
slide direction of subject 's finger occurs during collection of
partial images of a fingerprint, the rotational displacement can be
corrected, allowing an upright image to be reliably obtained. This
allows an upright image to be reliably obtained even when the slide
direction changes each time a finger slides and rotational
displacement is present in each of individual partial images of a
fingerprint. That is, it becomes possible for the device to be
insensitive to influence of the rotational displacement present in
the fingerprint image, which displacement changes depending on the
slide direction.
[0206] Further, a fingerprint image can be obtained as an upright
image even if the partial image of a fingerprint is collected when
the orientation of the fingerprint sensor 31 is changed, e.g., the
fingerprint authentication device 1 is rotated to an upside down
position and then used, and the fingerprint image can be collected
irrespective of the orientation of the fingerprint authentication
device 1 (fingerprint sensor 31), thereby allowing the device to be
highly convenient.
[0207] Additionally, the fingerprint image can be obtained as an
upright image regardless of the pointing direction (orientation) of
the fingerprint authentication device 1, display 81, and
fingerprint sensor 31 etc., and therefore there is no need for
detecting and determining the pointing direction (orientation) of
the fingerprint authentication device 1, display 81, and
fingerprint sensor 31, etc., thereby eliminating the need for
inclusion of functions (hardware, software) to detect and determine
such a pointing direction and reducing manufacturing cost.
[0208] Moreover, even when the collected fingerprint image is
displayed on the display 81, the device is able to display the
biometric information image so that the image is never affected by
rotation of the device, thereby easily providing visual
confirmation that the fingerprint image has been properly
obtained.
[0209] Further, it becomes possible that the degree of freedom of
direction of the sensor (fingerprint sensor, etc.) providing the
biometric information collection means 10 are higher during
mounting of the sensor and reduction in the mounting area of a
wiring pattern reduces the volume and price of the device.
[0210] FIGS. 17(a), 17(b) are diagrams to explain a relationship
between a wiring pattern and the mounting area of the pattern on
the fingerprint sensor 31, FIG. 17(a) is a diagram illustrating the
mounting area in the case of the wiring pattern length being short,
and FIG. 17(b) is a diagram illustrating the mounting area in the
case of the wiring pattern length being long. As can be seen from
FIGS. 17(a), 17(b), if the degree of freedom of mounting the sensor
can be made high and the sensor can be mounted on short wiring
setting when mounting of the fingerprint sensor 31 is performed,
the mounting area can be reduced.
[0211] Further, when the biometric information collection means 10
is a device of the type allowing biometric information to be read
by the biometric information collection means 10 being brought into
contact with a living body and further when the living body is
moving relative to the sensor and a living body site contacting the
sensor is rarely moved because of bending of outer skin of the
living body due to friction etc., in other words, pulling force
occurs between the sensor and living body, a movement direction of
the living body can be properly detected, allowing reliable
collection of biometric information.
[0212] For example, in a case where a subject to be authenticated
is unfamiliar to an operation of sliding his/her finger on the
sensor, it would probably be expected that the degree of a force to
be applied to move (slide) the finger becomes unsuitable and the
living body site contacting the fingerprint sensor 31 is hardly
moved because of bending of outer skin of the living body due to
friction, etc., in other words, pulling force occurs between the
sensor and living body. As such, even when the slide movement
instantly and temporarily stops, the device continuously allows
accurate detection of movement direction and enables even the
subject unfamiliar to the sliding operation to easily perform input
of biometric information.
[0213] Additionally, even when a rotational displacement between
the most preferable slide direction on the fingerprint sensor 31
and the movement direction of the finger occurs during collection
of biometric information, the device allows a display means 15 to
display biometric information (upright image) after correction of
the rotational displacement of information. In more detail, for
example, even when the degree of freedom of the using direction of
the biometric information collection means 10 is high, i.e., when
the biometric information collection means 10 is used in an upside
down position, the device allows the display means 15 to display an
upright image and further allows the high degree of freedom of the
mounting direction of the sensor providing the biometric
information collection means 10.
[0214] Moreover, even when the position of a living body site
relative to the biometric information collection means is detected
and the subject is prompted to move the living body site so that
the living body site is located in place, the device is able to
easily perform instruction, providing great convenience.
Additionally, even when the degree of freedom of the using
direction of the biometric information collection means 10 is high,
i.e., when the means 10 is used in an upside down position, the
device is able to properly instruct the subject to correct
positional displacement and further allows the high degree of
freedom of the mounting direction of the sensor providing the
biometric information collection means 10.
[0215] Additionally, performing authentication using biometric
information after correction of rotational displacement of the
information allows authentication process to be performed without
influence of rotational displacement during collection of biometric
information. For example, even when the orientation of the
fingerprint authentication device during enrollment of enrollment
data and the orientation of the fingerprint authentication device
during matching are significantly different, the device is able to
perform authentication without lowering its authentication ability,
thereby providing great convenience.
(B) Explanation of First Modification
[0216] FIG. 18 is a block diagram illustrating the functional
configuration of a first modification of the fingerprint
authentication device as one embodiment of the invention.
[0217] A fingerprint authentication device 101 is configured in
nearly the same way as in the first embodiment, except that a
biometric information central position detection means 21 is
provided instead of the position detection means 16 in the
fingerprint authentication device 1 of the first embodiment. Note
that in FIG. 18, the same numerals previously used designate the
same or nearly the same elements and therefore detailed explanation
thereof is omitted.
[0218] The biometric information central position detection means
21 is for detecting a central position of a partial fingerprint
image (biometric information) collected by the fingerprint sensor
31 (biometric information collection means 10). Note that as a
method for detecting the central position of partial image through
the use of the biometric information central position detection
means 21, a variety of methods previously described can be employed
and for example, when the biometric information is a fingerprint,
the technology disclosed in Japanese Patent Laid-Open No.
2002-109543) can be employed.
[0219] The instruction means 17 of the first modification is for
correcting difference information indicative of a difference
between a biometric information central position detected by the
biometric information central position detection means 21 and a
predetermined position on the fingerprint sensor 31, using
difference information indicative of a difference between a
movement direction detected by the movement direction detection
means 11 and a predetermined direction, and instructing and
prompting the subject to move his/her finger so that the subject's
finger is located in place on the fingerprint sensor 31.
[0220] In more detail, the instruction means 17 performs
instruction using difference information Dx, Dy indicative of
differences between biometric information central positions Bx, By
detected by the biometric information central position detection
means 21 and the corresponding central positions Cx, Cy on the
fingerprint sensor 31. That is, if Dx=Bx-Cx, Dy=By-Cy and
instruction directions are Ix, Iy, the resulting instruction
directions are determined as Ix=-Dx, Iy=-Dy, resulting from
inversion of the difference information Dx, Dy. In more detail,
when the finger of the subject is positioned to the right relative
to the fingerprint sensor 31, the instruction means 17 instructs
(guides) the subject to move his/her finger to the left.
[0221] Moreover, the instruction to the subject may be done, for
example, by displaying a mark indicating a direction as a
left-pointing arrow, etc., on the display 81. Further, in this
case, directional instruction is not displayed in a detailed
fashion, but only one chosen out of constituent instruction
directions and having a greater magnitude than the others is
displayed, for example, using a step size of 90 degrees.
[0222] Also in this case, when a rotational displacement is present
between the fingerprint sensor 31 and instruction means 17,
instruction on the display becomes meaningless and therefore the
displacement is corrected using difference information 9 indicative
of a difference between the movement direction detected by the
fingerprint sensor 31 from the biometric information and a
predetermined direction.
[0223] If corrected directions are Ix', Iy', they are calculated
using the following equation (13). ( I x ' I y ' ) = ( cos .times.
.times. .theta. - sin .times. .times. .theta. sin .times. .times.
.theta. cos .times. .times. .theta. ) .times. ( I x I y ) ( 13 )
##EQU5##
[0224] As described above, according to the fingerprint
authentication device 101 as the first modification of the
invention, action and effect similar to those of the first
embodiment are obtained and in addition, an effect that
authentication can be performed without influence of the rotational
displacement is obtained by allowing the device to perform
authentication using biometric information in which a rotational
displacement has been corrected. Further, even when the degree of
freedom of the using direction of the fingerprint sensor 31 is
high, i.e., when the sensor is used in an upside down position, the
device is able to properly instruct a user to correct a positional
displacement and in addition, the degree of freedom of the mounting
direction of the fingerprint sensor 31 becomes high, allowing the
device to be extremely practical for use.
(C) Explanation of Second Modification
[0225] For an information processing device provided with the
above-described fingerprint sensor 31 and display 81, it could be
proposed to move a cursor (pointer) displayed on the display 81
using the fingerprint sensor 31. That is, the fingerprint sensor 31
is allowed to function as a pointing device.
[0226] FIG. 19 is a block diagram illustrating the functional
configuration of a second modification of the fingerprint
authentication device as one embodiment of the invention. As shown
in FIG. 19, a fingerprint authentication device 102 of the second
modification includes the biometric information collection means
10, the movement direction detection means 11, the coordinate
conversion means 14, the display means 15, the storage means 22,
the biometric information movement direction correction means 40
(reference direction setting means 41), a movement distance
detection means 42, and a pointer movement control means 43. Note
that in FIG. 19, the same numerals previously used designate the
same or nearly the same elements and therefore detailed explanation
thereof is omitted.
[0227] The movement distance detection means 42 is for detecting
the movement distance of subject's (user's) finger with respect to
the fingerprint sensor 31, i.e., detecting a movement distance of
biometric information. The reference direction setting means 41 is
for setting up the reference direction to which the movement
direction of user's finger on the fingerprint sensor 31 refers and
the pointer movement control means 43 is for controlling the
movement of a pointer on the display means 15 based on the
reference direction set up by the reference direction setting means
41, the movement direction of a finger detected by the movement
direction detection means 11, and the movement distance of a finger
detected by the movement distance detection means 42.
[0228] The biometric information movement direction correction
means 40 includes the reference direction setting means 41 and is
for detecting and correcting the movement direction of a finger
with reference to the reference direction set up by the reference
direction setting means 41.
[0229] Displayed on the display means 15 is a cursor that moves in
response to a finger moving distance and the direction on the
fingerprint sensor 31.
[0230] Both FIGS. 20(a), 20(b) are diagrams illustrating examples
of appearance of the second modification of the fingerprint
authentication device 1 as one embodiment of the invention, FIG.
20(a) is a diagram illustrating an example of appearance of the
fingerprint authentication device 102 before modification, and FIG.
20(b) is a diagram illustrating an example of appearance of the
fingerprint authentication device 1 after modification.
[0231] Similarly to the fingerprint authentication device 1 of the
first embodiment, the fingerprint authentication device 102 shown
in FIGS. 20(a), 20(b) also includes the main body 1a provided with
the fingerprint sensor 31 and the display unit 1b provided with the
display 81, in which the main body and the display unit are
openably connected together through the two-axis hinge (nail
clipper hinge) 1c.
[0232] That is, the fingerprint authentication device 102 is
configured as a laptop personal computer having the fingerprint
sensor 31 mounted on the main body 1a and tailored to rotate the
display unit 1b by 180 degrees and then fold the same. In this
case, it is assumed that the display 81 is mounted so that the
direction of the display 81 is kept unchanged, regardless of
whether the device is used as shown in FIG. 20(a) or as shown in
FIG. 20(b).
[0233] Since in the fingerprint authentication device 102, the
subject (user) slides, during fingerprint authentication, his/her
finger on the fingerprint sensor 31 so that the finger is pulled
back in front of him/her, when the slide direction matches the
vertical/downward direction relative to the display 81, the subject
will be able to correct the movement direction of a finger.
[0234] Therefore, the device may be configured so that after the
coordinate conversion means 14 performs coordinate conversion on
the biometric information image such that the biometric information
image is reversed in the up/down or left/right direction based on
the slide direction, the device determines the movement direction
and movement distance. Or, when the device does not use the
biometric information image, the device may convert the detected
movement direction rather than the biometric information image.
[0235] That is, the fingerprint authentication device 102 is
configured so that in order to properly detect the movement
direction, the movement direction of a finger on the fingerprint
sensor 31 is previously input as a reference direction by the
reference direction setting means 41 and stored as a reference
value (initial value) to previously correct the movement direction
in the storage means 22 (initial value setting step), and the
movement direction is corrected using the set reference value
(correction step).
[0236] Then, how to correct the movement direction in the
fingerprint authentication device 102 as the second modification
will be explained with reference to flow charts shown in FIGS. 21
and 22. Note that FIG. 21 is a flow chart (steps F10 to F20) for
explanation of details of the initial value setting step, FIG. 22
is a flow chart (steps G10 to G40) for explanation of details of
the movement direction correction step.
[0237] In the initial value setting step, first, the movement
direction input as a reference direction is detected by the
movement direction detection means 11 (step F10), and then the
detected movement direction is stored as an initial value (initial
direction) in the storage means 22 (step F20), and the process is
terminated.
[0238] Further, in the movement direction correction step, the
movement direction is detected by the movement direction detection
means 11 (step G10) and the movement distance is detected by the
movement distance detection means 42 (step G20). Note that the
movement direction detection step and movement distance detection
step may be reversed in order or performed simultaneously.
[0239] Next, the biometric information movement direction
correction means 40 retrieves the initial value (initial direction)
stored in step F20 of the initial value setting step from the
storage means 22 (step G30) in order to calculate a difference
between the movement direction detected in step G10 and the initial
direction for correction of the movement direction (step G40). The
pointer movement control unit 43 controls a pointer so that it is
moved on the display in the corrected movement direction.
[0240] As described above, according to the fingerprint
authentication device 102 as the second modification of the
invention, the reference direction corresponding to the movement
direction of a living body site is previously set up as an initial
value and the movement direction of the living body site is
corrected using the initial value to allow the biometric
information collection means 10 to be used in various directions,
and even when the degree of freedom of the using direction of the
biometric information collection means 10 is high, the device is
able to properly detect the movement direction of the living body
site and to increase the degree of freedom of the mounting
direction the sensor providing the biometric information collection
means 10.
[0241] Accordingly, even if the fingerprint sensor 31 is used in an
upside down position or a lateral position when the fingerprint
sensor 31 is used as a pointing device, the pointer can be moved on
the display 81 in the direction input by the user.
[0242] Note that although in FIG. 19, the position detection means
16, the instruction means 17, the movement direction search range
reduction means 12, the movement stop detection means 13, the
feature extraction means 32, the matching degree calculation means
19, the matching degree determination means 20, the biometric
information central position detection means 21, the storage means
22 etc., are not illustrated for simplification, the device of the
invention is not limited to the configuration of FIG. 19, but may
include all of or at least a portion of the above components and
allow the corresponding components to function individually.
(D) Application Examples
[0243] Examples of applications of the fingerprint authentication
device of the invention will be shown below.
[0244] (1) Mobile Phone
[0245] FIGS. 23(a), 23(b), 23(c) are diagrams illustrating examples
in which the fingerprint authentication device of the invention is
applied to a mobile device (mobile phone) 200 provided with a sweep
fingerprint sensor and FIGS. 24(a), 24(b) are diagrams illustrating
examples of fingerprint images derived from images collected in the
states of FIGS. 23(b), 23(c).
[0246] The mobile device 200 shown in FIGS. 23(a) to 23(c)
incorporates a sweep fingerprint sensor 31 therein for the purpose
of inclusion of functions such as owner authentication. As a mobile
device such as a recent mobile phone is reduced in volume, how a
user holds the device changes in various forms. Particularly, since
the user holds the mobile phone by one hand, how the user holds the
phone is considered to easily change. At the time of enrollment,
the user was unfamiliar to sliding of his/her finger on the sensor,
but after tried matching several times, the user becomes familiar
to the sliding and in some cases, changes his/her way of holding
the phone.
[0247] FIGS. 23(a), 23(b) illustrate examples in which a rotational
displacement around the normal to a paper is present. In general,
although when a rotational displacement between enrollment data and
input data is present, authentication ability is reduced, according
to the invention, a fingerprint image is coordinate-converted so
that the slide direction points downward and therefore
authentication can be performed without a rotational displacement,
as shown in FIGS. 24(a), 24(b).
[0248] Note that the rotational displacement may be corrected by
coordinate converting the fingerprint image or by coordinate
converting the enrollment data or matching data. However, if the
fingerprint image is previously coordinate converted, the display
direction of images corresponding to the enrollment data and input
data becomes independent of the slide direction when the
fingerprint image is displayed.
[0249] (2) PDA
[0250] FIGS. 25(a), 25(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (PDA: Portable Digital Assistants)
provided with a sweep fingerprint sensor and a PDA 201 shown in
FIGS. 25(a), 25(b) incorporates thereon the sweep fingerprint
sensor 31 that is disposed in the vertical direction (90 degrees or
270 degrees).
[0251] The slide direction expected in the PDA 201 is the
horizontal direction and a user (subject) is able to input his/her
fingerprint using either his/her right or left hand.
[0252] (3) PDA
[0253] FIGS. 26(a), 26(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (PDA) provided with a sweep fingerprint
sensor and the configuration of the PDA 202 shown in FIGS. 26(a),
26(b) is similar to that after 90-degree rotation of the PDA 201
shown in FIGS. 25(a), 25(b), and the PDA 202 is usable even after
its 180-degree rotation.
[0254] The PDA 202 allows a user to input his/her fingerprint
irrespective of whether the device is rotated 180 degrees.
[0255] (4) PDA
[0256] FIGS. 27(a), 27(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (PDA) provided with a sweep fingerprint
sensor. A PDA 203 shown in FIGS. 27(a), 27(b) incorporates thereon
the sweep fingerprint sensor that is disposed on a surface opposing
the surface on which the display 81 of a main body 203a is formed.
The sensor is mounted in the vertical direction (90 degrees or 270
degrees).
[0257] The slide direction expected in the PDA 203 is the
horizontal direction and a user (subject) is able to input his/her
fingerprint using either his/her right or left hand.
[0258] (5) Laptop PC
[0259] FIGS. 28(a), 28(b) are diagrams illustrating examples in
which the fingerprint authentication device of the invention is
applied to a mobile device (laptop PC (Personal Computer)) provided
with a sweep fingerprint sensor and FIG. 28(a) is a diagram
illustrating a display unit 204b in an unfolded state, and FIG.
28(b) is a diagram illustrating a display unit 204b as a front unit
in a folded state.
[0260] The laptop PC 204 shown in FIGS. 28(a), 28(b) incorporates
thereon the sweep fingerprint sensor 31 adjacent to the display 81
of the display unit 204b in the horizontal direction, and further,
similarly to the fingerprint authentication device 1 shown in FIG.
12, a main body 204a and the display unit 204b provided with the
display 81 are openably connected together through a two-axis hinge
(nail clipper hinge) 204c.
[0261] Further, as shown in FIG. 28(b), the display unit 204b of
the laptop PC 204 is rotated about an axis "b" of the two-axis
hinge 204c and further folded through an axis "a", and when the
display unit is folded so as to allow the display 81 to serve as a
front of the PC, a screen to be displayed on the display 81 is
displayed in such a manner that the screen is rotated 180
degrees.
[0262] That is, although in the example shown in FIG. 28(a), the
sequence of letters "ABC" is shown as an upright image, even when
the display unit 204b is rotated about the axis "b" through the
two-axis hinge 204c and further folded by its rotation about the
axis "a", so as to allow the display 81 to serve as a front of the
PC, the sequence of letters "ABC" is displayed as an upright image,
as shown in FIG. 28(b).
[0263] Although in the laptop PC 204, the slide direction during
use in a folded state is reversed compared to that during use in an
unfolded state, the invention allows a user to input his/her
fingerprint independent of 180-degree rotation of the device.
[0264] According to the invention, the display orientation of the
display 81 is rotated 180 degrees and accordingly the slide
direction and the movement direction of a cursor are also displaced
180 degrees, but correction of movement direction is performed,
thereby causing the movement direction of the cursor not to rotate
by 180 degrees.
[0265] (6) Tablet PC
[0266] FIGS. 29(a), 29(b), 30 (a), 30(b) are diagrams illustrating
examples in which the fingerprint authentication device of the
invention is applied to a mobile device (tablet PC) provided with a
sweep fingerprint sensor, FIG. 29(a) is a diagram illustrating a
state where a tablet PC 205 is used in the vertical direction, FIG.
29(b) is a diagram illustrating a state where the tablet PC 205 is
used in the horizontal direction, FIG. 30(a) is a diagram
illustrating a state where a tablet PC 206 is used in the vertical
direction, and FIG. 30(b) is a diagram illustrating a state where
the tablet PC 206 is used in the horizontal direction.
[0267] The tablet PC 205 shown in FIGS. 29(a), 29(b) incorporates
thereon the sweep fingerprint sensor 31 aligned with the
longitudinal direction of the display 81 of a device main body and
the tablet PC 206 shown in FIGS. 30(a), 30(b) incorporates thereon
the sweep fingerprint sensor 31 aligned with the minor side
direction of the display 81 of the device main body.
[0268] Further, the tablet PCs 205, 206 can be disposed so that the
PCs are rotated 90 degrees or 270 degrees in response to the
display orientation of the display. The tablet PCs 205, 206 allow a
user to input his/her fingerprint independent of 90-degree,
180-degree, 270-degree rotation of the device.
[0269] Further, when as shown in FIG. 29(b), the tablet PC 205 is
used in a horizontal direction, i.e., used in such a manner that it
is rotated 90 degrees in a clockwise direction from the tablet PC
being used in a vertical direction as shown in FIG. 29(a), a screen
to be displayed on the display 81 is rotated 90 degrees and
displayed.
[0270] That is, although in the example shown in FIG. 29(a), the
sequence of letters "ABC" is displayed as an upright image, even
when the tablet PC 205 is rotated 90 degrees in a clockwise
direction from its current state, the sequence of letters "ABC" can
be displayed as an upright image, as shown in FIG. 29(b).
[0271] Likewise, when as shown in FIG. 30(b), the tablet PC 206 is
used in the horizontal direction, i.e., used in such a manner that
it is rotated 90 degrees in a clockwise direction from the
orientation of the tablet PC being used in the vertical direction
as shown in FIG. 30(a), a screen to be displayed on the display 81
is rotated 90 degrees and displayed.
[0272] That is, although in the example shown in FIG. 30(a), the
sequence of letters "ABC" is shown as an upright image, even when
the tablet PC 206 is rotated 90 degrees in a clockwise direction
from its current state, the sequence of letters "ABC" can be
displayed as an upright image, as shown in FIG. 30(b).
[0273] Further, when the device is disposed so that the slide
direction points in the up/down direction, or left/right direction,
enrolling previously any one or more out of ten fingers of a
subject, or any one or more out of both thumbs, respectively,
allows the device to maintain a strong authentication performance
even if the device is disposed so as to change the disposing
direction.
[0274] Note that although the tablet PC 205 shown in FIG. 29(a) is
provided with the fingerprint sensor 31 on the right side of the
display 81, the tablet PC of the invention is not limited to this
configuration, but for example, may be provided with the
fingerprint sensor 31 on the left side of the display 81, meaning
that various modifications may be made without departing from the
scope of the invention. Further, when the tablet PC is provided
with the fingerprint sensor 31 on the left side of the display 81,
90-degree rotation of a main body in a clockwise direction will
cause the fingerprint sensor 31 to be positioned on the upper side
of the display 81.
[0275] Likewise, although the tablet PC 206 shown in FIG. 30(a) is
provided with the fingerprint sensor 31 on the upper side of the
display 81 on the paper, the tablet PC of the invention is not
limited to this configuration, but for example, may be provided
with the fingerprint sensor 31 on the lower side of the display 81
on the paper, meaning that various modifications may be made
without departing from the scope of the invention. Further, when
the tablet PC is provided with the fingerprint sensor 31 on the
lower side of the display 81 on the paper, 90-degree rotation of a
main body in a clockwise direction will cause the fingerprint
sensor 31 to be positioned on the left side of the display 81 on
the paper.
[0276] Additionally, when these tablet PCs 205, 206 are to be
rotated, the main body may be rotated in a counterclockwise
direction.
(E) Others
[0277] It should be noted that the invention is not limited to the
foregoing embodiments, but various modifications may be made
without departing from the scope of the invention.
[0278] For example, in the foregoing embodiments, although the
cases in which an object to be used for authentication is the
finger of a person and a fingerprint image is collected as
biometric information have been explained, the invention is not
limited to these cases, but may be applied, in a manner similar to
the above described cases, to the cases in which a palm print image
or blood vessel image is collected as biometric information from a
palm to be identified, producing action and effect similar to the
above described cases.
[0279] It is expected that one of ordinary skill, when guided by
the concepts and principles disclosed in the embodiments of the
invention, will be readily capable of implementing and
manufacturing the invention.
[0280] The fingerprint authentication device of the invention is
suitable for use in personal authentication systems typified by
compact information devices having insufficient space available to
incorporate a sensor, such as a mobile phone and PDA, and is
considered to have extremely high usefulness.
* * * * *